Add preference window

[zenangst]

The application should most definitely have a preference window where the user should be able to configure the following:

• [ ] Open main window on launch
• [ ] Run in Dock/Menubar or both
• [ ] Timeout delay between hotkey invocations
• [ ] Location of the configuration file

There are probably more things that we want to add here

[olemikkel]

Might be a known issue as this issue isn't completed, but the current preference window is unable to be moved for me (it also starts outside my screen).

[zenangst]

Yeah, I've noticed some funny business with that window.